A significant infrastructure of sensor and control networks operates through distributed intelligence and communication systems. Over the last 25+ years the industrial and commercial industries for sensory and control automation have used methods of multiplexing digital signals to minimize the number of wires installed in a control network. More particularly, the industry of data communication networking has evolved from a point to point RS-232 single server/many terminal (client) topology into a cloud-based interconnection of devices that strive to become a ubiquitous “web of devices.”
Today we think of this ubiquity as the Internet. However, there are actually thousands of sub-networks below the Internet and in parallel with the Internet that contain independent communication systems related to human interface as well as machine interface. Many of these machine-to-machine (M2M)/non-Internet networks are closed systems that do not have a seamless method of connecting to an outside network.
One of the primary existing interfaces for closed-system networks is RS-485 (EIA-485), which is a differential voltage communication interface that has become extremely popular for M2M interface applications over the last 25+ years and uses UTP (unshielded twisted pair) wires in order to provide low to medium speed signaling to many nodes of an embedded network. This is typically accomplished by having a single master node communicating with several slave nodes on a single pair of wire (two conductors) that “multi-drop” between the master and the multiple slaves. This type of communication is generally referred to as serial communication and specifically half-duplex (two wire) RS-485 networking. One example of this method would be modbus serial protocol/communication.
RS-485 can be found today on most real-world industrial and commercial equipment that operates in a distributed communication mode of functionality. This means that the overall RS-485 system operation gains its effectiveness and flexibility of operation by allowing the system to be configured and connected with many possible connections of devices to sense, monitor and control the sub-systems of an overall closed-system through the communication protocol(s) and communication interface(s) that the system designer envisioned.
One of the down sides of a closed system is that it is not designed to allow seamless integration to an open-system philosophy, which is increasingly desired and demanded by industry markets today (e.g., devices connecting to the Internet, outside networks, or mobile devices). As these industries evolved over the last two decades, many additional wish-list items have been added to the needs of industrial and commercial embedded networking. Many of the solutions over the last decade have migrated toward Internet accessibility as a general goal within the marketplace.
One of the current methods that many industries are migrating toward today is IP enabling their devices so that the advantages of ubiquity over the Internet can be exploited by currently manufactured closed-systems or legacy installations of closed systems. Internet Protocol (IP) enabling is the concept of allowing a device (machine, human interface device, etc.) to network/interact with other IP enabled devices in a relationship of server/client, peer-to-peer or other conceptual system interconnections.
The idea of IP connectivity is that every closed-system, sub-network, or device (based on the application or desired functionality) is assigned an IP Address that gives the connection point a unique method of identification. Examples of connections to devices are TCP/IP, UDP and many other OSI 7 layer network model standards driven concepts. The overall intent is that any IP-enabled device could, in theory, communicate to and from any other IP enabled device provided there is sufficient communication intelligence local to the device and the method of identifying each device.
Internet accessibility has most commonly been accomplished by using Ethernet as an information technology (IT) solution for networking multiple nodes using CAT5 cabling. The use of Ethernet for networking consists of the use of TCP/IP for Internet Protocol access which allows remote access as well as Local Area Network (LAN) functionality. Internet and other outside access can be implemented by adding an IP-enabled Ethernet jack (802.3 RJ-45), a WiFi (802.11) wireless, or other interfaces such as Bluetooth, Zigbee, LIN, CAN, etc.
However, this migration of installations using both RS-485 with UTP cabling and CAT5 for Ethernet has caused a disconnect between the goals and installation methods of the two different network methodologies. Ethernet networking over CAT5 cabling is an evolution from office computing and IT professionals. This often means that specialized network professionals are needed on-site during installation to install, configure and verify the proper operation and connections of the Ethernet network.
RS-485 systems are often successfully implemented by trained electricians (not network specialists) and the cabling is much simpler and minimized due to the multi-drop methods of connecting the UTP cable. There is a general trend today toward both the local control benefits of RS-485 as well as expansion of the capabilities (and global access) of Ethernet and TCP/IP communication within industrial and commercial networks. In addition, supervisory control and data acquisition (SCADA) systems are abundantly deployed in the industrial and commercial markets. Many of these SCADA systems today are being forced or persuaded by the market to transition to Ethernet interfaces.
Many devices have been created today that attempt to combine the use of RS-485 (or serial data networks) along with TCP/IP (Ethernet IP networks). These devices utilize a technique of serial data tunneling that converts the image of serial data packets into Ethernet frames and transports the serial data as packets via TCP/IP or UDP data over the Ethernet CAT5 cabling. This solution attempts to eliminate UTP RS-485 cabling and migrates toward solely using CAT5 cables.
In addition, most closed systems that communicate between addressed devices or nodes within the closed system utilize a simplified addressing method that is very similar to IP addressing but is typically limited to a much smaller number of nodes on the closed-system network. Typical networks can be found with maximum nodes of four, eight, sixteen, or thirty-two nodes (based on the original RS-485 specification). There are also RS-485 network evolution types that support up to 256 nodes per twisted-pair bus.
Many manufacturers have recognized the desire to interconnect and expand closed systems and market them as Internet accessible by utilizing converters and gateways. A common gateway application is the allow RS-485 closed-systems to gain ubiquitous access to an IP-Enabled Internet Access. A common use of this gateway application is to create web-page access through the Internet to monitor and edit parameters on the closed system. The gateway is often seen by the closed system as a slave node or more directly becomes the master node of the closed system.
Because closed systems were originally designed to be secure, reliable and consistently functional as guaranteed-by-design due to the nature of being closed to the outside world, once system designers move away from this core belief the overall system design begins to fragment in its cohesion of reliability and predictability of operation. As the desire to become flexible, scalable and ubiquitous grows, the M2M industries are becoming more aware of the complexities of reliability of operation, security of data, scalability of their solutions, and legacy support of their core competency strengths within their industry. The nature of data protocol conversion and transport through IP-enabled systems is often a tradeoff between gaining flexibility and Internet access and decreasing reliability, security and forced system redesign.
One of the characteristics of RS-485 to IP-enabled transport is the latency (or delayed delivery of bytes/packets) due to the dissecting, reformatting and non-native transport of the data payloads within the IP (typically Ethernet frames of data). The problems are at multiple levels. First, the natural latency of delayed delivery of packets can cause unstable or undesirable operation because the original closed-system design expects the network to perform in a deterministic manner with consistent network timings. Second, many RS-485 data protocols utilize time-based packet delimiting as a mechanism for separating and identifying the information on the native RS-485 serial network. This is a serious problem when attempting to incorporate data converters that transport IP-enabled Ethernet frames. The RS-485 serial network is operating on a cadence or heartbeat of synchronized activity of bits, bytes and packet frames. An example of this protocol usage is modbus serial RTU and is widely used in industrial and commercial M2M networks.
Thus, one of the key problems that arises with this technique is that data latency (bit to bit, byte to byte and frame continuity) is rarely maintained and cannot maintain delivery within specification of the network requirements. Many systems would benefit from maintaining the low-latency management of UTP while evolving to Ethernet TCP/IP (without the use of data tunneling or serial data converters).
Related problems arise in the powerline communication or current-carrier communication systems used in smart grid applications. More particularly, there are reliability issues due to localized noise from back splatter or inductive kickback because of switching power supplies, motors, ballasts, etc. In addition, there are problems of unstable noise-floor energy throughout power infrastructure and varying attenuation causing dynamic signal-to-noise ratios because of unknown distances between nodes throughout the power system's infrastructure. The noise-filtering techniques used today for delivering power and energy data filter high frequencies by bypassing the high frequencies across the powerlines or shunting the unwanted signals through filtering devices.
However, this shorting out of the unwanted frequencies on the power wires in an effort to leave only the clean, low-frequency component of the power waveform causes a bypass or shunt of the unwanted frequencies within the power wire's frequency spectrum. That is problematic when the higher frequencies of the power infrastructure need to be used for additional purposes other than powering the devices, such as energy data communication and management. As described herein, exemplary embodiments solve these problems by enabling power distribution over a baseband data universe to devices needing electricity while also facilitating transmission of power or energy data over one or more broadband data universes. This is important because efficient distribution of power, management of energy usage and demand response capability has become very important in view of the growing population and the intensifying problem of global warming.
Accordingly, there is a need for contiguous packet delivery and low-latency delivery of byte frames (often with very few bytes i.e. <32) when processing real-time and/or closed-loop sensory and control systems. There is also a need for efficient distribution of power over a baseband to devices needing electricity while also facilitating transmission of power or energy data over one or more broadband channels for management of energy usage and demand response capability. More generally, there is a need for a system that maintains low-latency management of UTP when combined with Ethernet TCP/IP networks.